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Shutemov" To: Yu-cheng Yu Cc: x86@kernel.org, "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann , Andy Lutomirski , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin , Weijiang Yang , Pengfei Xu , Haitao Huang , "Kirill A . Shutemov" Subject: Re: [PATCH v25 19/30] mm: Update can_follow_write_pte() for shadow stack Message-ID: <20210423102522.5djgt2fb3unsidnw@box.shutemov.name> References: <20210415221419.31835-1-yu-cheng.yu@intel.com> <20210415221419.31835-20-yu-cheng.yu@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210415221419.31835-20-yu-cheng.yu@intel.com> X-Stat-Signature: 5uurtr7y74ysbt6reszmds34mpfzfrci X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: BF6336000123 Received-SPF: none (shutemov.name>: No applicable sender policy available) receiver=imf09; identity=mailfrom; envelope-from=""; helo=mail-lj1-f171.google.com; client-ip=209.85.208.171 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1619173517-693586 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Apr 15, 2021 at 03:14:08PM -0700, Yu-cheng Yu wrote: > Can_follow_write_pte() ensures a read-only page is COWed by checking the > FOLL_COW flag, and uses pte_dirty() to validate the flag is still valid. > > Like a writable data page, a shadow stack page is writable, and becomes > read-only during copy-on-write, but it is always dirty. Thus, in the > can_follow_write_pte() check, it belongs to the writable page case and > should be excluded from the read-only page pte_dirty() check. Apply > the same changes to can_follow_write_pmd(). > > While at it, also split the long line into smaller ones. > > Signed-off-by: Yu-cheng Yu > Cc: Kees Cook > Cc: Kirill A. Shutemov > --- > v25: > - Split long line into smaller ones. > v24: > - Change arch_shadow_stack_mapping() to is_shadow_stack_mapping(). > > mm/gup.c | 16 ++++++++++++---- > mm/huge_memory.c | 16 ++++++++++++---- > 2 files changed, 24 insertions(+), 8 deletions(-) > > diff --git a/mm/gup.c b/mm/gup.c > index ef7d2da9f03f..f2813cf4d07b 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -356,10 +356,18 @@ static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address, > * FOLL_FORCE can write to even unwritable pte's, but only > * after we've gone through a COW cycle and they are dirty. > */ > -static inline bool can_follow_write_pte(pte_t pte, unsigned int flags) > +static inline bool can_follow_write_pte(pte_t pte, unsigned int flags, > + vm_flags_t vm_flags) > { It might be cleaner to pass down vma pointer and dereference it within the function: can_follow_write_pte(vma, pte, gup_flags). Otherwise looks good to me: Reviewed-by: Kirill A. Shutemov -- Kirill A. Shutemov